Should a ranged attack originate from the front 180 degrees of a base of a model equipped with a shields, the models armour save is increased by plus two (5+ base if no other armour) instead of the usual plus one (6+ base if no other armour). No cost increase will be incurred for shields.
The reason for this is to encourage the use of shields and assist in making hand weapons and shields the norm as opposed to two hand weapons. As the standard rules stand, almost everyone opts for dual hand weapons with no penalty which assumes that everyone in the Warhammer Old World is ambidextrous. Having read much feedback about off-hand penalties, dual wield penalties, and other such solutions I have deduced that the simplest one is to simply offer a viable alternative. Hence the above rule.